Overview

According to the concept of ego depletion, sometimes called strength model of self-control, any activities that demand a sense of self-control--inhibiting or overriding impulses, regulating emotions, or reaching difficult choices and decisions--utilizes resources or energy from a single, limited supply (Baumeister, Bratslavsky, Muraven, & Tice, 1998). When individuals engage in an act that demands self control, this supply diminishes, and a state called ego depletion prevails. This state impairs the capacity of individuals to enact other activities that demand self control. After a period of recovery or some other interventions, this supply is restored, and the capacity of individuals to demonstrate self control is reinstated.

Indeed, numerous studies have shown that individuals who execute tasks that demand self control are, subsequently, less able perform other tasks that demand self control (e.g., Muraven, Tice, & Baumeister, 1998). For example, after individuals ignore or evade another colleague--often referred to as the silent treatment--their persistence on both cognitive and physical tasks subsequently declines (Ciarocco, Sommer, & Baumeister, 2001).

Many researchers believe that any activities in which individuals must exert control to override prepotent or natural responses, usually to fulfill some goal or standard, is assumed to deplete resources from a limited supply (e.g., Vohs, Baumeister, Schmeichel, Twenge, Nelson,& Tice, 2008). This capacity to demonstrate self control might have evolved to resolve conflicts between natural impulses and cultural imperatives (Baumeister & Vohs, 2007).

Other defining features of self control have been delineated. In addition, self control represents behaviors that incur immediate costs, such as aversive emotions, but future benefits (vanDellen & Hoyle, 2010). Furthermore, self control always entails a conflict between competing desires (vanDellen & Hoyle, 2010).

Conflict management theory, developed by Botvinick, Braver, Barch, Carter, and Cohen (2001), specifies the contexts that deplete resources. In particular, according to conflict management theory, in some instances, individuals experience an inclination to initiate two conflicting responses simultaneously. They might, for example, feel the need to either fight or flee. This conflict is recognized by the anterior cingulate cortex (Botvinick, Nystrom, Fissell, Carter, & Cohen, 1999). Activation of this region mobilizes resources, represented in the dorsolateral prefrontal cortex, that can be used to inhibit undesirable behaviors.

Manipulations of ego depletion

Clerical tasks

A variety of protocols and techniques have been deployed to deplete the resources that are assumed to facilitate self control. One of the most common protocols involves a clerical task (e.g., Baumeister, Bratslavsky, Muraven, & Tice, 1998; DeWall, Baumeister, Gailliot, & Maner, 2008). In a typical study, participants might receive a page of text. These individuals are instructed to cross out each occurrence of the letter e--a letter than usually appears frequently in the text. Subsequently, these participants receive another page of text. On this occasion, they are instructed to cross out each occurrence of the letter e, except if this letter is followed by a vowel or is embedded in a word in which a vowel appears two letters earlier. This protocol ensures that participants must suppress the inclination to cross out every letter e--an inclination that is established while in the previous phase.

This task has been shown to impair subsequent performance on tasks or activities that demand self control (e.g., Baumeister, Bratslavsky, Muraven, & Tice, 1998). For example, relative to individuals who are merely instructed to cross out every letter e, participants who complete this more demanding activity are subsequently less inclined to offer assistance to a stranger in need (DeWall, Baumeister, Gailliot, & Maner, 2008).

Writing essays

To deplete the resources that are utilized to curb impulses, some researchers instruct participants to write a short essay. Specifically, to deplete resources, some participants are told to abstain from the letters A and N, which are common letters and thus difficult to avoid. In the control condition, participants are told to abstain from the letters X and Z, which are rare letters and easier to avoid (see Schmeichel, 2007).

A similar task, administered by Muraven, Shmueli and Burkley (2006), has also been used to deplete self regulatory resources. In this task, participants are asked to retype a passage. To deplete these resources, some of these participants are then instructed to continue this process except to refrain from pressing the letter ?e? or the space bar. The remaining participants continue without this instruction. Participants who needed to refrain from letter ?e? or the space bar were, subsequently, less able to resist an urge.

The mirror tracing technique

Mirror tracing, a task administered by Quinn, Brandon, and Copeland (1996), is also sometimes utilized to deplete resources from this limited supply of effort. Typically, individuals need to trace some geometric figure. To deplete resources, participants trace this figure with their non-dominant hand, permitted only to watch their hand in a mirror. In the control condition, the figure is traced with the dominant hand and participants are permitted to watch their hand directly.

Fennis, Janssen, and Vohs (2009) showed this task does indeed consume resources from this limited supply of effort. After some participants traced this figure while watching their hand in a mirror, they become more susceptible to sales tactics. That is, they were more willing to donate to a cause if, earlier, the person who proposed this request had offered a compliment.

Inhibition of extraneous stimuli

Fischer, Greitemeyer, and Frey (2008) utilized a paradigm in which some participants were instructed to disregard extraneous stimuli (for similar manipulations, see Gilbert, Krull, & Pelham, 1988; Schmeichel, Vohs, & Baumeister, 2003). In this study, participants watched a series of video clips. A series of words appeared towards the bottom of this screen. To deplete limited resources, some participants were explicitly instructed to disregard these words--a task that demands self control. The remaining participants received no instructions about these words. This technique to deplete resources amplified the confirmation bias, indicating the procedure was effective.

Perceived depletion of mental energy

When people are misled to believe they have exhausted their mental energy or self-regulatory resources, their performance on subsequent tasks that demand effort diminishes (Clarkson, Hirt, Jia, & Alexander, 2010). That is, perceived depletion, rather than actual depletion, is sufficient to compromise performance. Presumably, when people believe they have depleted their mental energy, they feel the need to conserve any resources that may be available. They are not as likely to mobilize effort on subsequent tasks.

Clarkson, Hirt, Jia, and Alexander (2010) conducted studies that demonstrate the effect of perceived depletion on subsequent performance. In one study, participants completed a task in which they needed to identify specific letters in a text. Then, some participants were informed that several features of this task, such as the background color, have been shown to deplete mental energy. Other participants were informed these features have been shown to replenish mental energy. Finally, participants completed a series of anagrams. If participants were informed their resources had been depleted, instead of replenished, they were not as likely to persist with these anagrams. They were, presumably, conserving their resources. Three other studies replicated this pattern of results.

Interrupted tasks

Sometimes, individuals are interrupted just before they complete a task. These interruptions significantly reduce the likelihood that individuals can maintain self control on subsequent activities, as shown by Freeman and Muraven (2010).

In particular, as a goal or target approaches, individuals become especially absorbed in this activity and motivated to finish. That is, in these instances, only momentary effort--sometimes lasting a few minutes--is needed to fulfill this goal. Individuals usually feel significantly more content after a goal is fulfilled. This brief effort, therefore, will generate significant outcomes. Individuals thus feel especially motivated to mobilize this effort and complete the task (Freeman & Muraven, 2010).

While they are so engaged in the activity, they cannot as readily withhold their effort. That is, when interrupted, they need to concentrate carefully to desist from this task. This concentration depletes resources, curbing their capacity to complete other tasks that demand this mental energy (Freeman & Muraven, 2010).

Freeman and Muraven (2010) undertook several studies that validate these arguments. In one study, participants first completed a task in which they needed to sort cards. Midway during this task, the participants were interrupted and asked to undertake another activity instead. Some of these participants were interrupted towards the beginning, within two minutes of a task that demands about five minutes to complete. Other participants were interrupted towards the end, after four minutes.

Next, participants completed a task that assesses the level of resources that were depleted. A series of numbers appeared, over 12 minutes. Participants pressed a space bar whenever the sequence 6 and 4 appeared. When participants were interrupted 1 minute, rather than 3 minutes, before completing a task, their performance on the subsequent activity declined. That is, their resources had been depleted.

The second study was similar, except another task was administered to assess ego depletion: Participants were asked to solve a series of anagrams, of few of which were unsolvable. If participants were interrupted immediately before completing one task, they were not as persistent on the unsolvable anagrams, again implying these resources had been depleted.

The third study was also similar, except participants first completed a word search task. They had to uncover a series of words from a matrix of letters and were interrupted after uncovering either 3 or 8 of the 10 possible words. In addition, after they were interrupted, participants completed a measure of executive functioning: the Tower of Hanoi problem. If participants had been interrupted after almost completing the word search task?-that is, after uncovering 8 of the 10 words?-they needed longer time to solve the Tower of Hanoi problem.

This finding does uncover some practical implications for managers. When employees have nearly completed a task, interruptions should be minimized. Perhaps, for example, these employees should be permitted to work in a quiet location, for an hour or so.

Uncertainty about the future

When people feel a sense of uncertainty about the future, they exhibit the signs of ego depletion. For example, they are more likely to indulge rather than develop knowledge (Milkman, 2012).

For example, in one study, conducted by Milkman (2012), participants received a lottery ticket. Next, they completed a series of challenging arithmetic equations. If participants had been permitted to scratch the ticket before completing these equations--and thus circumvented any uncertainty--they showed greater persistence. That is, they dedicated more time to the arithmetic equations, indicating that perhaps their mental energy had not been depleted.

Similarly, in a second study, some participants were not sure which of two pizzas they would receive, because one pizza may not be available. Other participants did not experience this uncertainty. If participants experienced uncertainty, they were more likely to choose an unhealthy dessert rather than healthy dessert--often reminiscent of ego depletion. In another study, even writing about a time that prompted certainty or uncertainty generated the same pattern of results. A final study showed that measures of ego depletion mediated the relationship between uncertainty and the tendency to yield to temptations.

Arguably, uncertainty increases the need of individuals to monitor the environment vigilantly. In addition, individuals may attempt to suppress feelings of uncertainty, which can also deplete resources.

Envy

Individuals often feel envious, especially when they interact with someone who is fortunate, wealthy, and successful. According to Hill, DelPriore, and Vaughan (2011), envy actually affects the cognitive processes of individuals. Specifically, when people experience envy, their attention tends to be directed to these envied individuals but not to other individuals. However, their mental energy is consumed, compromising their capacity to complete other tasks.

These possibilities were explored by Hill, DelPriore, and Vaughan (2011). In one study, to evoke envy, some university students wrote about four occasions in which they felt envious towards a friend or acquaintance. In the control condition, other participants wrote about daily activities. Next, participants read an interview between a student and journalist . The student was the same sex as the participants, as well as similar in age, and answered questions about their career goals and the location they would like to live. Next, they completed a distraction task. Finally, they received a series of questions designed to assess their memory of the interview.

If participants felt envious, they spent more time reading the transcript of the interview. After controlling for reading time, they were also more likely to remember details of this interview. Envy, therefore, seemed to direct attention to details about a peer.

In the second study, participants read six interviews, each between a student and journalist. The students were portrayed as low, moderate, or high in wealth. In addition, a photo accompanied each transcript. The students in the photo were either attractive or unattractive. After reading each interview, participants indicated the degree to which they felt various emotions. Some of these emotions corresponded to envy, including resentment, hostile, and envious. Participants also rated the students on five personality traits. Finally, they answered questions that assess their memory of the interviews.

Again, feelings of envy increased both the time that participants dedicated to reading the transcript and the memory of these transcripts. Wealthy students provoked more envy in both sexes. Attractive students provoked more envy, but only in female participants. Furthermore, as shown in the third study, only envy, rather than admiration, mood, or arousal, corresponded to this memory of details. The final study showed that envy diminished the time that individuals dedicated to an anagram task. In short, envy distracts attention from tasks that are not related to evaluating other people.

Attempting to cultivate justice

Managers often attempt to demonstrate procedural justice. For example, they may seek the opinions of subordinates, suppress their biases when they reach decisions, and offer individuals the opportunity to appeal these decisions. In addition, managers may attempt to demonstrate interactional justice. They may, for instance, treat subordinates with respect and share information. As Johnson, Lanaj, and Barnes (2014) showed, when managers demonstrate procedural justice, their capacity to maintain self-control later diminishes. That is, the implementation of procedural justice depletes self-regulatory resources. In contrast, the implementation of interactional justice replenishes self-regulatory resources.

To illustrate, in one study, 82 managers completed surveys twice a day over 10 days. First, this survey assessed the degree to which these individuals demonstrated procedural and interactional justice. Then, they completed questions that assess how depleted these feel, answering questions like "Right now, it would take a lot of effort for me to concentrate on something". Finally, they answered questions that assess mood, personality, and their tendency to help colleagues.

As hypothesized, procedural justice at one time was positively associated with depletion at a subsequent time, whereas interactional justice at one time was negatively associated with depletion at a subsequent time. Depletion was negatively associated with the tendency to help colleagues, called organizational citizenship behavior.

Arguably, procedural justice depletes resources because, to implement such behaviors, individuals need to inhibit their natural tendencies and biases. Interactional justice may replenish resources because social interactions are rewarding, instilling a sense of inclusion rather than exclusion.

Consequences of ego depletion

Helping

Ego depletion tends to impede helping and altruism, at least towards strangers. That is, after individuals engage in tasks that demand self control and the inhibition of their natural inclinations, they become less inclined to offer help towards disadvantaged strangers (DeWall, Baumeister, Gailliot, & Maner, 2007).

To illustrate, in one study, conducted by DeWall, Baumeister, Gailliot, and Maner (2007), some participants engaged in a task that demands self control. Specifically, these participants received a page of text and were instructed to mark each occurrence of the letter e--a letter than appeared frequently in the text. Next, they received another page of text. Again, they were instructed to mark each occurrence of the letter e, except if this letter was followed by a vowel or was embedded in a word in which a vowel appeared two letters earlier. In other words, participants needed to override their inclination mark every letter e, which had been established earlier.

These individuals, compared to participants who merely marked each occurrence of the letter e, showed a reduced tendency to offer help in various scenarios. That is, participants read six hypothetical scenarios in which they were granted an opportunity to donate money or to offer assistance. The scenarios revolved around donating money to a homeless person, donating money to children with terminal illness, offering a car ride to an unfamiliar classmate, providing directions to a lost person, lending a mobile telephone to someone, and offering food to a homeless person. For each scenario, participants were asked to specify the likelihood they would help in these situations, on a scale from 1 to 9.
Participants who marked only a specific subset of the letter e were less inclined to help in these scenarios (e.g., DeWall, Baumeister, Gailliot, & Maner, 2008).

Similarly, in a subsequent study, another activity that demands self control--watching a video while disregarding some words that appeared towards the bottom of this screen--also diminished the subsequent inclination to help (e.g., DeWall, Baumeister, Gailliot, & Maner, 2008). Interesting, this effect dissipated if participants had earlier consumed a drink containing glucose, which putatively restores the depleted resources. Accordingly, this effect of disregarding words on subsequent helping can be ascribed to the depleted resources, which coincides with the inhibition of natural inclinations.

These findings imply that helping a stranger does demand self control--and, thus, a need to override the prevailing inclinations of individuals. This observation is intriguing because many authors have shown that helping does fulfill many personal needs, such as the alleviation of guilt and the approval of peers (see Baumeister, 2005; Cialdini, Brown, Lewis, Luce, & Neuberg, 1997; Cialdini & Kenrick, 1976). Furthermore, helping can also be motivated by a sense of empathic concern (Batson, Duncan, Ackerman, Buckley, & Birch, 1981; Batson, Sager, Garst, Kang, Rubchinsky, & Dawson, 1997). Nevertheless, the possible costs and risks of helping, such as embarrassment or injury, might offset these benefits and foster the inclination to withdraw from prosocial acts (e.g., Garcia & Harrison, 2007). As a consequence, helping tends to involve the suppression of these inclinations.

However, tasks that demand self control do not curb the likelihood that individuals will want to help a family member (DeWall, Baumeister, Gailliot, & Maner, 2008). This finding implies that helping a family member does not demand appreciable self control. This observation is consistent with inclusive fitness theory, as proposed by Hamilton (1964). In particular, individuals share appreciable genetic overlap with kin. Natural selection favors attributes that promote the perpetuation of these genes. Thus, through natural selection, individuals exhibit tendencies to promote the survival of kin. Indeed, many studies confirm that individuals are more inclined to help family members (Madsen, Tunney, Fieldman, Plotkin, Dunbar, Richardson, et al., 2007). Hence, the assistance of kin might not demand significant self control or inhibition of natural inclinations.

Susceptibility to sales tactics

After individuals engage in activities that demand self control, they become more susceptible to sales tactics (Fennis, Janssen, & Vohs, 2009). Specifically, sales employees apply a variety of tactics to persuade customers. They might apply a technique, called foot in the door, in which their initial request is modest, such as "Would you sign your name to this petition", but their subsequent request is steeper, such as "Would you also donate $100 to this cause" (Burger, 1999; Freedman & Fraser, 1966). Alternatively, they might utilize the door in the face approach, in which customers are exempted from a specific impediment or prohibition (Cialdini, Vincent, Lewis, Catalan, Wheeler, & Darby, 1975). Furthermore, they might apply the lowball technique in which customers receive a request that initially seems modest but, after acquiescing, discover that compliance is steep (Burger & Petty, 1981).

Research shows these techniques are effective--but primarily when customers operate in a mindless state (Langer, 1992), dedicating negligible effort to the decision. When customers do not deliberate carefully, they invoke various heuristics or simple principles, such as "Reciprocate generous behavior". Accordingly, individuals become more susceptible to sales tactics (Cialdini, 1993).

Indeed, according to Fennis, Janssen, and Vohs (2009), astute sales employees often ask a sequence of requests. The first request is intended to demand careful deliberation, consuming resources from a limited supply of effort or energy. When these resources are depleted, customers do not consider subsequent decisions carefully. They generate fewer counterarguments. They invoke simple heuristics in lieu of considered deliberation. As a consequence, they might become more susceptible to particular sales tactics.

To investigate these propositions, Fennis, Janssen, and Vohs (2009) first conducted a series of studies to show that initial requests do indeed consume resources from a limited supply of effort or energy. In Study 1, some of the participants first received a request that demanded some deliberation. They were asked a series of questions about their personal eating habits, such as their consumption of saturated fat, whole bran, and vegetables. Other participants did not receive this request. Subsequently, all participants were instructed to generate arguments against their initial position on some topic (Fennis, Janssen, & Vohs, 2009).

Relative to the other participants, individuals who received the initial request generated fewer counterarguments. These findings are consistent with the proposition that initial requests consume resources, which in turn impairs the capacity to uncover counterarguments.

In a subsequent study, some participants engaged in a task that demands considerable effort. Other participants engaged in a relatively simple activity. Next, the experimenter exempted some of the participants from a tedious activity--a mathematics task. Finally, participants were asked whether or not they are willing to assist in future research.

Interestingly, after participants engaged in a demanding activity, they were especially susceptible to the sales tactics of experimenters. That is, if these individuals were exempted from a monotonous task, they were particularly likely to participate in future research (Fennis, Janssen, & Vohs, 2009).

Cheating

Self control is also needed to override the temptation to cheat. In other words, after individuals engage in a task that demands self control, they subsequently become more inclined to cheat.

To illustrate, in a study conducted by Mead, Baumeister, Gino, Schweitzer, and Ariely (2009), some participants engaged in a task that demanded self control. Specifically, they were instructed to write an essay, while avoiding two common letters: A and N. Other participants engaged in a task that demanded minimal self control. They were instructed to write an essay, while avoiding two rare letters: X and Z.

Next, participants undertook a task, in which an opportunity to cheat was available. A matrix of numbers was presented. The task was to uncover pairs of numbers that sum to 10. The experimenter, ostensibly, did not count the number of answers that were uncovered. Instead, participants specified the number of answers they uncovered in an empty box, then paid themselves one quarter for each correct answer, before destroying the answer sheet.

If participants had evaluated themselves, participants who had engaged in the task that demands self control were more likely to allocate themselves many quarters. If the experimenter evaluated participants instead, this pattern did not emerge. These findings indicate that self control subsequently increases the likelihood of cheating.

The same pattern emerged when another task was undertake to manipulate self control--a Stroop task. Taken together, these findings indicate that cheating might represent a natural, inherent response in many individuals. To align with social expectations, individuals need to curb this impulse--which demands self control. Ego depletion will thus compromise this capacity to curb cheating.

Forgiveness

Interestingly, if mental energy is depleted, individuals are more likely to forgive people for minor offences (Stanton & Finkel, 2012). That is, when people are mildly offended by a person--such as when someone arrives a few minutes later--they feel a natural inclination to forgive. Nevertheless, if they begin to contemplate the offence carefully, they may become aware of the problems and complications that could have arisen. Their resentment may grow, and forgiveness may be impeded.

This possibility was confirmed by Stanton and Finkel (2012). In their study, individuals completed the Stroop task in which they needed to name the color of a word sequence. To deplete mental energy, for some participants, the words were incongruent with the color, such as blue written in a red font. For other participants, the words were congruent with the color. Next, participants imagined that someone in their life committed severe offences, such as infidelity, or mild offences, such as failing to telephone when promised. Finally, participants indicated whether they would forgive this behavior. If mental energy had been depleted, participants were more likely to forgive minor, but not severe, offences.

Self enhancement

Ego depletion might curb some of the traditional self enhancement biases (for a discussion, see Fischer, Greitemeyer, & Frey, 2007). That is, to improve their mood states, individuals often overestimate their abilities and attributes. They will, for example, often feel their qualities are superior to the traits of a typical person, called the above average effect (Taylor & Brown, 1988). Second, they often feel they can control random forces, like a roulette wheel (Taylor & Brown, 1988). Third, they do not feel they are vulnerable to undesirable events, such as skin cancer or vehicle crashes, called an optimism bias (Weinstein, 1980). Collectively, these above average effects, sense of control, and optimism biases are designated as positive illusion biases (Taylor & Brown, 1988).

To maintain these biases, individuals must deliberately shift their attention and memory from their limitations and concerns to their strengths and opportunities. This shift in attention and memory demands self control. Accordingly, after individuals undertake other tasks that demand self control, and thus deplete the requisite resources, individuals may be less likely to demonstrate these positive illusion biases (Fischer, Greitemeyer, & Frey, 2007).

Indeed, Fischer, Greitemeyer, and Frey (2007) confirmed this proposition. For example, after individuals attempted to suppress their emotions after watching a disturbing movie, they become less likely to feel their qualities were superior to the attributes of a typical person. They also felt less inclined to believe they would prevail in a game of chance.

Cognitive performance

Ego depletion impairs performance on some, but not all, cognitive tasks. Theoretically, ego depletion should impede performance only on tasks that demand the inhibition of prevailing inclinations. Schmeichel, Vohs, and Baumeister (2003) showed that ego depletion, as a consequence of tasks that demand self control, subsequently impaired performance on an activity that involved logical reasoning. However, ego depletion did not impede performance on tasks that involved memorizing and subsequently recalling nonsense syllables or familiar information.

The capacity to withstand anxiety

After the mental effort of individuals is depleted, feelings of anxiety are more likely to impair performance on various tasks. In contrast, if mental effort is not depleted, anxiety tends to be unrelated to performance. In particular, this mental energy enables individuals to inhibit their worries and, thus, preserve their performance.

Bertrams, Englert, Dickhauser, and Baumeister (2013) conducted a series of three studies that confirm these arguments. In the first study, participants first wrote a short passage. To deplete mental energy, some of these individuals were also instructed to avoid the letters e and n. Next, these individuals completed a task in which they needed to memorize a series of nonsense words. Finally, the levels of anxiety they experienced were also assessed. If mental energy had been depleted, anxiety was inversely related to performance on the memory task. In contrast, if mental energy had not been depleted, anxiety did not seem to be related to performance on the memory task.

The next two studies replicated and extended this finding. The same pattern of observations, for example, was uncovered when the task comprised arithmetic questions rather than memory. Furthermore, in one study, participants were asked to indicate the extent to which they felt distracted or worried during the task. If mental energy had been depleted, these distractions or worries were especially likely to compromise performance. These findings, taken together, indicate that anxiety provokes worries, and these worries impede performance, unless individuals can mobilize the mental energy that is needed to inhibit or prevent these distractions.

Intentionality bias

When mental resources are depleted, and deliberate processing is hampered, the prevailing cognitive inclinations of individuals, such as the intentionality bias, might become more pronounced (Begue, Bushman, Giancola, Subra, & Rosset, 2010). The intentionality bias refers to the inclination of individuals to overrate the extent to which the behavior of someone else might be intentional (Rosset, 2008)--and this tendency might be amplified when the behavior is harmful (Knobe, 2003). For example, an inadvertent bump is sometimes interpreted as an intentional provocation.

Usually, the first response of individuals is to assume the behavior is intentional. After some delay, if individuals consider the issue further, they might recognize the act was inadvertent (Rosset, 2008). That is, they reflect upon alternative causes.

This contention was substantiated by Begue, Bushman, Giancola, Subra, and Rosset (2010). In this study, in the context of a food tasting test, participants received either significant, modest, or no alcohol. Furthermore, regardless of whether or not they received alcohol, half of the individuals were told they had consumed alcohol. Next, participants read a series of sentences about simple actions. Examples include "He deleted the email" or "She made a mark on the paper". Finally, they were asked to decide whether these actions were intentional or accidental. Alcohol increased the likelihood that actions were perceived as intentional.

Decision preferences

After individuals complete a task that depletes self-regulatory resources, they are more likely to adopt a concrete construal (Wan & Agrawal, 2011; see construal level theory). That is, they are more likely to focus their attention on the specific, concrete features of objects or events rather than on broad, intangible concepts. To illustrate, when they decide whether to complete a task, they are more likely to consider the specific actions?-a tangible feature?-instead of the underlying purpose?-an intangible concept.

In particular, when self-regulatory resources or mental energy is depleted, individuals feel exhausted. They need to uncover more efficient means to fulfill their goals at that time. That is, they may need to change their specific plans and activities. However, they do not need to change their more enduring goals. Transient periods of exhaustion should not affect the feasibility of more enduring goals. Consequently, they direct their attention to tangible actions and features instead of abstract goals and concepts (Wan & Agrawal, 2011).

Wan and Agrawal (2011) conducted a series of studies that validate these arguments. In one study, the mental energy of some participants was not depleted: They merely needed to delete the es from an article. The mental energy of other participants was depleted: They performed the same task, except some complex rules were also introduced to decide which es to delete. Next, all participants completed the behavior identification form, developed by Vallacher and Wegner (1989), in which individuals need to choose one of two alternatives to describe various actions: a concrete or abstract option. If mental energy depleted, participants choose the concrete alternative. They regarded the act of ringing a doorbell, for example, more as moving a finger than determining whether someone is home.

Study 2 was similar except, after deleting the es, participants were asked to choose between two jobs: an interesting but difficult job or an uninteresting but easier job. If mental energy had been depleted, rather than not depleted, participants were more willing to accept the uninteresting but easier job. They disregarded interest or values?-an intangible, abstract concept. Their decision depended more on the logistics or activities-?a more concrete, tangible feature.

In Study 3, a different task was used to deplete mental resources. On each of the 60 trials, participants received information about two products. To deplete resources, they needed to choose which of two products they prefer. In the control condition, the participants merely specified which of these products they have used before. Next, the individuals needed to decide between a restaurant with excellent food but an inspiring view or a restaurant with only adequate food but an excellent view. If resources had been depleted, participants became more inclined to choose the restaurant with adequate food but an excellent view. When individuals adopt a concrete construal, they sometimes overestimate the importance of incidental features, such as the view, because they cannot compare diverse considerations effectively.

In Study 4, some individuals attempted to suppress their negative emotions, a task that is sometimes used to deplete mental energy. Next, they chose between two calendars. These calendars were identical except one option showed one week to a page and the other option showed one month to a page. If mental energy had been depleted, participants preferred one week to a page. Because they did not adopt an abstract construal, these individuals focussed on more specific or immediate times, such as a week instead of a month.

As Study 5 discovered, when individuals were encouraged to adopt an abstract construal, these effects of ego depletion subsided. Thus, ego depletion tends to evoke a concrete construal, which can be overcome by methods that elicit an abstract construal.

Exhaustion

Goldberg and Grandey (2007) argued that ego depletion?-and, specifically, the motivation to regulate or conceal emotions?-could provoke exhaustion, which can culminate in burnout. Specifically, according to Goldberg and Grandey (2007), individuals are often compelled to display positive emotions when they interact with customers. Hence, they need to display emotions that diverge from their underlying affective state or inclinations, which should demand self control. As a consequence, the imperative to display positive emotions should deplete resources, undermining the capacity of individuals to engage in other tasks that demand self control. Individuals, therefore, must consume more of these resources to function, which is manifested as exhaustion.

To assess these predictions, Goldberg and Grandey (2007) undertook a study in which participants completed a simulation task, reminiscent of call centers. Some participants were instructed to exhibit positive emotions. They were, for example, told to "express friendliness, warmth and enthusiasm and show positive emotion". Other participants were instructed to act authentically rather than to follow specific imperatives. They were told, for instance, "if you get irritated or stressed, handle it however you want--just relax and be yourself".

After interacting with customers, participants who had been instructed to exhibit positive emotions reported exhaustion. That is, they reported feeling "emotionally drained", "used up", and "burned out". In addition, they subsequently committed more errors on a difficult clerical task.

Factors that restore depleted resources

The ingestion of glucose

Various studies have shown that specific resources, conditions, and states can replenish the supply of limited resources. For example, some studies have shown that consumption of glucose can replenish these stores (e.g., DeWall, Baumeister, Gailliot, & Maner, 2007; Gailliot, Baumeister, DeWall, Maner, Plant, Tice, et al., 2007).

To illustrate, in the study conducted by DeWall, Baumeister, Gailliot, and Maner (2007), some participants engaged in an activity that demands self control and thus depletes resources from a limited supply. In particular, while watching a video, these participants were instructed to direct their attention away from words that appeared near the bottom corner. Other participants did not have to control their direction of attention.
Participants who had to shift their attention from the words were, subsequently, less inclined to commit towards helping a disadvantaged person. Presumably, because the resources to engage in self control were depleted, their capacity to override their natural inclination to withdraw from altruistic acts was limited.

Interestingly, however, this pattern of observations was observed only in participants who had pearlier consumed a drink that primarily contains an artificial sweetener, called Splenda, with no glucose, which was 0 calories. This pattern was not observed in participants who had previously consumed a drink containing glucose, which was 140 calories. That is, these individuals offered assistance even after engaging in a task that depleted these resources. Glucose offset the effects of ego depletion, even though the two drinks were rated as equally pleasant by participants.

The discovery that glucose consumption restores the resources that facilitate self control is consistent with the role of this chemical in the brain. Glucose is especially likely to be consumed by brain activities that involve the resolution of conflicting processes (Laughlin, 2004). Self control usually involves reconciling personal inclinations with societal imperatives (Baumeister & Vohs, 2007) and thus should demand appreciable levels of blood glucose as demonstrated by (Fairclough & Houston, 2004).

The efficiency of glucose use

The capacity of individuals to utilize glucose efficiently may also override the effect of ego depletion. Thus, individuals with symptoms of Type 2 diabetes--who cannot utilize glucose efficiently--may be more likely to demonstrate limitations in self control.

DeWall, Pond, and Bushman (2010) substantiated this possibility. These researchers examined whether symptoms of Type 2 diabetes compromise forgiveness--an act that demands self control because individuals need to inhibit or override any impulse to avenge some transgression.

In one set of studies, for example, participants completed a scale that assessed the extent to which they exhibit the symptoms of Type 2 diabetes, such as shortness of breath at night or numbness in the feet. Next, participants completed various measures of forgiveness. One measure assessed the general tendency of individuals to forgive friends, relatives, or colleagues. Another measure assessed the willingness of individuals to forgive someone in five hypothetical situations, such as violating confidentiality. A third measure gauged the extent to which participants had actually forgiven someone after a past transgression. Symptoms of Type 2 diabetes were negatively correlated with each measure of forgiveness.

Rinsing the mouth with carbohydrates

The benefits of ingesting carbohydrates have been ascribed to the benefits of glucose and energy: That is, after people ingest carbohydrates, levels of blood glucose increase and mental energy thus escalates. Molden, Hui, Scholer, AMeier, Noreen, D?Agostino, and Martin (2012) proposed, and then validated, an alternative account. According to their proposal, when carbohydrates are detected in the mouth, the dopaminergic pathways in the striatum are activated, promoting motivation. Presumably, throughout evolution, humans have learnt to associate this sensation in the mouth with the prospect of rewards and energy. This account implies that glucose does not need to be ingested to override ego depletion.

Molden, Hui, Scholer, AMeier, Noreen, D?Agostino, and Martin (2012) conducted a series of studies that verify this account. In the first study, participants read a message and were instructed to delete each e. In one condition, to increase the level of mental energy that is depleted, some participants were also told not to delete the es that are next to a vowel or one letter from a vowel. Next, these individuals completed an anagram task. Furthermore, their levels of blood glucose were at various times with a very accurate method, in contrast to previous studies that relied on an Accu-Chek blood glucose monitor. Levels of ego depletion did not reduce glucose levels but did compromise persistence on the anagram task.

In the second study, participants again complete the task in which they needed to delete es and only some of these participants were also told not to delete the es that are next to a vowel or one letter from a vowel. Then, participants rinsed their mouths with a solution that contained either carbohydrates or an artificial sweetener. Finally, they were told to clench a handgrip for as long as possible. If mental energy had been depleted by the difficult variant of e deletion task, participants could clench the handgrip for a longer period after rinsing their mouths with carbohydrates instead of an artificial sweetener. The third study showed the same pattern of results even when a cognitive task was included instead of the handgrip. The final study confirmed that blood glucose levels do not rise after individuals rinse their mouths with carbohydrates.

Positive emotions

Positive affect can also replenish these depleted resources. This proposition was uncovered by Tice, Baumeister, Shmueli, and Muraven (2007). In this experiment, participants were instructed to inhibit a specific impulse or thought during a period of 5 minutes. Specifically, they were told to abstain from any thoughts about a white bear--a task that depletes resources.

Participants were then granted a five minute break. Some participants watched a comedic movie clip during the break. Other participants either sat quietly or watched a sad movie clip.

Both before abstaining from thought about a white bear, as well as after the break, participants were instructed to squeeze a handgrip. If participants had watched no movie clip or a sad movie clip during the break, their capacity to maintain this grip deteriorated after suppressing particular thoughts. In contrast, if participants had watched a comedic movie during the break, this capacity remained intact.

According to Tice, Baumeister, Shmueli, and Muraven (2007), these findings demonstrate that positive affect might replenish these depleted resources. Additional studies replicated these findings, but using other tasks to measure ego depletion, such as consuming a revolting drink, and other activities to consume these resources, such refraining from chocolate.

Optimism

If people tend to be optimistic, and this tendency is primed or activated in some way, self-regulatory resources tend to be restored. That is, optimism can override the effects of ego depletion (In Den Bosch-Meevissen, Peters, & Alberts, 2014).

For example, in one study, conducted by In Den Bosch-Meevissen, Peters, and Alberts (2014), participants first completed an arithmetic task. As predicted, if the task was challenging rather than simple, these individuals performed less effectively on a subsequent activity in which they needed to lift a specific weight for an extended period of time. That is, the challenging questions depleted resources and thus compromised performance on a task that demands effort. However, if two conditions were fulfilled, these challenging questions did not compromise performance on the lifting task. In particular, if participants reported elevated levels of optimism, and also were exposed to synonyms of optimism, confidence, and hope, this ego depletion effect dissipated.

Presumably, when individuals feel depleted and exhausted, optimism declines even in people who are usually optimistic. Nevertheless, cues that correspond to optimism can prime or reinstate this optimism. Once people feel optimistic, they imagine that favourable consequences could unfold. These images could evoke positive emotions, and positive emotions might restore mental energy. Alternatively, because of this optimism, individuals feel more confident they can mobilize all their self-regulatory resources. That is, they do not feel they need to withhold some of this effort to accommodate unexpected exigencies.

Watching TV and social surrogates

As Derrick (2013) showed, when people watch their favorite TV show, with family and beloved characters, their capacity to sustain self-control improves. Specifically, these characters operate like social surrogates; that is, many of their social needs, such as a sense of belonging, interest, and excitement, are fulfilled. When these needs are fulfilled, the corresponding positive emotions may restore mental energy and enhance self-control. Indeed, unlike actual social interactions, these social surrogates do not deplete mental energy either: Effort is not needed to attend closely to social cues or inhibit inappropriate remarks or emotions.

In one study, participants wrote about a recent trip. To deplete mental energy, some of these participants were also instructed to refrain from the letters a and i during this task. Next, participants wrote about either their favorite TV show, to foster a sense of social surrogacy, or the objects in the room. Finally, these individuals completed a measure of creativity--the remote associates task--as well as a measure of mood. In general, refraining from the letters a and i during the writing task impaired performance on the measure of creativity, unless participants were granted an opportunity to write about their favorite TV show.

Perspective taking

After people imagine somebody who is similar to them engaging in an activity that restores energy, such as napping during the day, they also feel more restored. That is, ego depletion diminishes, and the capacity of these individuals to complete tasks that demand effort increases.

In this study, some but not all participants completed a task that depletes mental energy: They attempted to avoid thinking about a white bear for five minutes. Next, they heard a story about a person who either napped or did not nap during a work day. They were encouraged to adopt the perspective of this person. Finally, they completed an anagram task in which they needed to rearrange letters to form words. Some of the items were impossible. Persistence on this task reflected the degree to which their mental energy had been restored. As predicted, if mental energy had been depleted, participants who adopted the perspective of someone else napping were more persistent on the anagram task than other participants.

The second study was similar, except other procedures were utilized to deplete mental energy, to restore energy, and to assess subsequent depletion. For example, to restore energy, participants imagined someone consuming a caffeinated drink. The same pattern of observations was observed provided that students imagined another student consuming the drink. If students imagined a professor consuming the drink, mental energy was not restored. Thus, only perspective taking of people in the same community is effective. When people observe someone in another group, they are not as likely to experience the same states as this individual.

Abstinence from smartphones at night

Because sleep facilitates the recovery of mental effort or self-regulatory resources, any events or circumstances that impair sleep should impede this recovery. Smartphones have been shown to impair sleep as well as exacerbate ego depletion and compromise work engagement.

In particular, the detrimental effect of smart phones on sleep can be ascribed to two mechanisms. First, outdoor and indoor light can activate neurons in the suprachiasmatic nuclei of the hypothalamus, and these neurons can inhibit the release of melatonin from the pineal gland. This decrease in melatonin curbs sleepiness. Even light pulses behind the kneecap can affect the circadian rhythm (Campbell & Murphy, 1998). Second, smartphones are often used to engage in tasks that are mentally stimulating, such as conversations about work. Consequently, smartphones may diminish the extent to which individuals feel disengaged from work, promoting arousal, also compromising sleep.

Consistent with these premises, Lanaj, Johnson, and Barnes (2014) showed that smartphone use does indeed compromise the sleep and work engagement of individuals. That is, if individuals utilize smartphones for more than an hour or so after 9 PM, they tended to sleep fewer hours at night. Consequently, they were more likely to feel drained and depleted in the morning, compromising their level of engagement at work. These findings were observed after controlling time spent either watching TV or using tablets and computers after 9 pm. Nevertheless, if employees felt they had been granted a sense of autonomy and control over how to complete their work activities, this sense of depletion was not as likely to compromise engagement.

Moderators of ego depletion effects

After individuals read words, such as persist, persevere, endure, discipline, and so forth--or observe photographs of individuals who seem robust and vigorous--self control on one task becomes less likely to compromise self control on a subsequent activity, as shown by Alberts, Martijn, Greb, Merckelbach, and de Vries (2007). These words or photographs activate unconscious self representations, or memories, of occasions in which individuals felt persistent and determined. Conceivably, these activated self representations foster the expectation of exemplary self control, ultimately enhancing performance.

After individuals watch a comedy video or receive an unexpected gift, and thus experience positive affect, they also remain more persistent even after earlier having to suppress their natural impulses or thoughts.

Self affirmation

Indeed, other interventions have been shown to improve the capacity of individuals to maintain self control. Specifically, self affirmation, in which individuals reflect upon the achievement and pursuit of their values and priorities, enhances this capacity (Schmeichel & Vohs, 2009)

To illustrate, in the study conducted by Schmeichel and Vohs (2009), some participants first engaged in a task that demanded self control. Specifically, they wrote an essay, but were instructed to refrain from using the letters a or n.

Next, to manipulate self affirmation, participants ranked a series of 11 values and characteristics in order of importance. Then, some participants wrote about an occasion in which the value ranked number 1 was especially important, to evoke self affirmation. Other participants wrote about an occasion in which the value ranked number 7 might be important to someone else, representing a control condition.

Finally, the capacity of participants to withstand pain was assessed. Writing an essay, while refraining from specific letters, tended to impair intolerance to pain--because both activities demand self control, which is limited. Self affirmation, however, tempered this effect of writing the essay while refraining from specific letters. Accordingly, self affirmation must enhance the capacity to inhibit inclinations and to demonstrate self control.

Schmeichel and Vohs (2009) also examined the mechanisms that might underpin these benefits. They showed that self affirmation fosters an inclination to focus attention on broad, abstract concepts rather than specific, tangible features. This focus, in turn, tends to promote self control.

Beliefs about willpower

Job, Dweck, and Walton (2010) confirmed that individuals who perceive willpower as unlimited are not as likely to demonstrate the traditional effects of ego depletion. In their first study, participants completed a questionnaire that gauges whether or not they assume that impulse control and mental energy is limited in capacity. Typical questions were "Your mental stamina fuels itself; even after strenuous mental exertion you can continue doing more of it". Next, some of the participants completed a task that demands inhibiting natural inclinations--a task that putatively depletes mental energy. Finally, participants completed a task to ascertain whether or not their mental energy was depleted. Specifically, the Stroop task, in which they had to name the color of words rather than read these items, was administered.

In general, the first task that was intended to deplete mental energy compromised performance on the subsequent Stroop task. This deleterious effect of the first task dissipated, however, if participants assumed that mental energy is unlimited. The next study was the same, except the experimenters manipulated whether or not mental energy is assumed to be limited or unlimited. In particular, to prime the belief that mental energy is limited, some participants completed questions that refer only to the possibility this supply of resources is finite. Conversely, to prime the belief that mental energy is unlimited, other participants completed questions that only refer to the possibility this supply of resources is infinite. Again, when participants believed that mental energy is unfettered, one demanding task did not compromise performance on a subsequent activity (Job, Dweck, & Walton, 2010).

The next study explored the mechanisms that underpin the effect of these assumptions. As Job, Dweck, and Walton (2010) revealed, if participants assumed that mental energy is unlimited, their performance continued to remain exemplary on two subsequent tasks. Thus, these individuals did not merely dedicate undue effort to the second task. Furthermore, this assumption did not affect the degree to which the first task was perceived as exhausting. However, when participants assumed that mental energy is unlimited, exhaustion was unrelated to subsequent performance. That is, these individuals performed effectively even if exhausted.

Conceivably, mental energy is not quite as limited as many people believe. That is, in some contexts, the assumption that mental energy is finite could undermine persistence, even when such resources have not been depleted.

However, other studies indicate that beliefs about willpower cannot entirely overcome the effects of ego depletion. That is, if people believe that effort is unlimited, they might simply utilize most of their mental energy. But, once this mental energy is entirely depleted, beliefs about willpower cannot override ego depletion (Vohs, Baumeister, & Schmeichel, 2012).

To illustrate, Vohs, Baumeister, and Schmeichel (2012) replicated the studies that were conducted by Job, Dweck, and Walton (2010), with one amendment. Participants completed 0, 2, or 4 depleting and exhausting tasks before their effort on two other activities was assessed. For example, participants who completed four depleting tasks needed to choose between two similar products, complete a Stroop task, stifle their emotions after watching a comedy, and complete a letter crossing task. As predicted, if participants completed only two depleting tasks, they could maintain their effort on subsequent activities, provided they believed that willpower is unlimited. However, if participants completed only four depleting tasks, they could not maintain their effort on subsequent activities--regardless of whether or not they believed that willpower is unlimited. Beliefs about willpower no longer influenced performance.

Accessibility of role models

Exposure to someone who exhibits exemplary self control could, potentially, curb the effects of ego depletion. Certainly, studies show that such exposure can, at least, improve self control.

According to vanDellen and Hoyle (2010), when individuals are exposed to someone who typically demonstrates exemplary self control, their own level of self control escalates. In one study, conducted by vanDellen and Hoyle (2010), some participants were asked to reflect upon a friend who demonstrates excellent self control. Other participants were asked to reflect upon a friend who demonstrates deficient self control. Both before and after this exercise, all participants were asked to squeeze a hand grip for as long as possible. Compared to participants who reflected upon someone who tends to exhibit limited self control, participants who reflected upon someone who tends to exhibit exemplary self control squeezed the hand grip over a more extended time.

In a second study, also conducted by vanDellen and Hoyle (2010), carrots and cookies were presented to participants. Some of the participants were instructed to refrain from the cookies and eat the carrots instead. Other participants were instructed to eat the cookies. Furthermore, some participants watched the other individuals eat the carrots or cookies.

To assess self control, all participants then completed the Stroop task. That is, a list of words, representing colors like red, green, and blue, appeared in fonts of various hues. Participants were instructed to specify the color of this font rather than read the word. Usually, when the word is incongruent with the color, reading time is prolonged, called Stroop interference. If self control is elevated, this interference diminishes. In this study, after participants watched someone refrain from the cookies, but eat the carrots instead, interference diminished and thus self control was elevated.

In the third study, participants specified the name of two people they know: One of these people exhibits excellent self control and can resist temptations; the other person exhibits deficient self control and cannot resist temptations. Next, participants completed a lexical decisions task, in which strings of letters appeared. Participants had to decide whether or not each string was a legitimate word. Before each string, the name of these two people appeared subliminally.

Finally, participants completed another word task--the Remote Associates Test. Interestingly, if participants had been subliminally exposed to the name of a person who exhibits excellent self control during the lexical decision task, they showed more persistence on the Remote Associates Test.

In short, these studies indicate that individuals, when exposure to someone who exhibit self control, will more likely exhibit this self control themselves. This exposure increases the accessibility of mechanisms associated with self control (vanDellen and Hoyle, 2010).

Nevertheless, in some instances, vicarious exposure to self control is not beneficial. If individuals identify closely with someone who has exerted themselves, adopting the perspective of this person, they also feel exhausted. Their self control dissipates (Ackerman, Goldstein, Shapiro, & Bargh, 2009). In contrast, if participants merely reflect upon someone who exerts self control, without adopting the perspective of this person, their self control improves.

Monitoring their performance

If a clock is accessible, the effects of ego depletion seem to dissipate (Wan & Sternthal, 2008). To clarify, after mental energy is depleted, individuals become less likely to monitor their performance: They are not as inclined to compare their progress with some standard. Without this feedback, any sense of urgency declines and effort subsides.

When the time of day is more accessible, however, individuals are more prone to monitoring their progress. They become more aware of any deterioration in their performance, offsetting this decline in effort.

Wan and Sternthal (2008) undertook a series of studies that confirm these hypotheses. In each study, participants first engaged in a task that was intended to deplete negligible or appreciable resources. For example, to deplete negligible resources, participants were told to skim a document to identify, and then to cross out, each instance of the letter e. To deplete appreciable resources, participants completed the same task, but were instructed to skip letters that fulfilled specific criteria, such as es that appeared alongside another vowel.

Next, participants completed a numerical puzzle that demands persistence. Specifically, the last few puzzles of this task were actually unsolvable, unbeknownst to participants. The time that participants dedicated to this task was regarded as a measure of persistence.

In general, if participants had completed one activity that depleted appreciable resources, they were subsequently not as persistent on the numerical puzzle. However, if a clock was visible while they completed this puzzle, this effect of resource depletion diminished. Subsequent studies were similar, but showed that people who naturally self monitor their performance were also not as impaired by depleted resources.

Nevertheless, undue monitoring can also compromise self control. That is, as Strimas and Dionne (2010) argue, if individuals monitor themselves too frequently, they become more aware of their shortfalls, evoking negative emotions and sometimes compromising their confidence and effort.

Strimas and Dionne (2010) undertook a study that verifies this argument. In this study, people were asked to weigh themselves either every day or every week over 12 weeks. In addition, the extent to which they often feel concerned about their weight was also assessed. Interestingly, for individuals who often feel concerned about their weight, weight was more likely to diminish if they weighed themselves every week rather than every day. Indeed, if they weighed themselves every day, these participants became heavier over the 12 weeks. If they weighed themselves only once a week, these participants became lighter over this period.

Self awareness

If individuals experience a sense of self awareness, orienting attention to themselves, the effects of ego depletion diminish. That is, as Alberts, Martijn, and de Vries (2010) showed, after individuals who experience this self awareness complete a demanding task, their capacity to maintain self control on a subsequent activity remains intact.

To illustrate, in a study conducted by Alberts, Martijn, and de Vries (2010), participants completed a task that depletes mental energy from a limited supply. Specifically, over eight minutes, participants answered a series of arithmetic calculations. Some of these participants completed difficult calculations and were distracted by noise, depleting considerable resources. Other participants completed easier calculations and were not distracted by noise, depleting negligible resources.

Next, participants completed a sentence unscrambling task. To induce self awareness, for some of the participants, the sentences always began with the word "I". In the control condition, the word "I" was excluded. Finally, hand grip strength was measured before and after these tasks.

If participants performed the difficult calculations and were distracted by noise, their hand grip strength diminished considerably over time. However, if the participants had also been exposed to the word "I", representing a form of self awareness, this decline was not observed.

Conceivably, when individuals experience a sense of self awareness, they are especially inclined to compare their performance or behavior to some standard, such as a target. Because these comparisons are especially salient, individuals are more inclined to monitor and regulate their behavior to fulfill this standard.

Prayer

Prayer has been shown to prevent or diminish the depletion of mental energy or self-control. To illustrate, after people attempt to suppress their emotions while watching an emotional or amusing video, their performance on subsequent tasks that demand self-control tends to dissipate. They do not perform the Stroop task as well, for example: That is, they cannot easily name the font color of words that represent a contradictory color. However, if people pray before watching this video, this effect of suppressing emotions on Stroop performance is no longer significant, as Friese and Wanke (2014) showed.

The mechanisms that underpins the benefits of prayer are not certain. According to Friese and Wanke (2014), prayer might orient attention from immediate concerns to broader aspirations, and this construal has been shown to enhance self-control. Alternatively, prayer might prime thoughts around a source of strength or power. Finally, prayer entails a social interaction with god, and most social interactions have been shown to energize people and replenish resources. The study, however, uncovered support only to this last mechanism: The degree to which people felt they were in touch with someone mediated the association between prayer and Stroop performance.

Self-control strategies

As Dvorak and Simons (2009) showed, the self-control strategies that people apply can also influence the effect of ego depletion. Specifically, when individuals contemplate the future, enjoy solving problems, and devote effort into their thinking, the effects of ego depletion tend to diminish. In contrast, if individuals attempt to distract themselves, prefer immediate gratification, and behave impulsively, the effects of ego depletion do not diminish.

In particular, in one study, participants completed various measures that gauge self-control strategies. Three of these scales related to strategies that were assumed to be effective: future time perspective (e.g., "Thinking about the future is pleasant to me"), problem solving (e.g., "...I do something to try to solve the problem"), and cognitive effort (e.g., "...I try to see the problem in a different way"). Three of the scales related to strategies that were assumed to be ineffective, such as distractibility (e.g., "I am easily distracted from my school work"), poor delay of gratification (e.g., "When I really want something, I cannot keep my mind off it"), and impulsivity.

,

Later, some but not all participants completed a task that was designed to deplete resources: They were asked to suppress their emotions while they watched an emotional movie. Then, their persistence on another task, in which they needed to solve anagrams was assessed. Furthermore, at various times, blood glucose was measured.

In general, if participants suppressed their emotions, they were not as persistent in their attempt to solve anagrams. They resigned prematurely. Blood glucose levels partly mediated this effect. However, if participants applied the strategies that were assumed to be effective, such as future time perspective, this effect of suppression on persistence diminished.

Construal as work or fun

As Laran and Janiszewski (2010) showed, tasks that are construed as work tend to deplete resources. That is, after individuals undertake activities they conceptualize as a work obligation, their capacity to complete subsequent tasks that demand self control diminishes. Interestingly, however, tasks that are construed as fun do not tend to deplete resources Indeed, after individuals complete activities they conceptualize as fun, their capacity to undertake subsequent tasks that demand self control actually improves The completion of a fun task seems to increase vitality.

In one study, participants completed a task in which they needed to evaluate the physical properties of small amounts of two candies: Skittles and M&Ms. The individuals needed to follow specific instructions, such as to hold one Skittle for 30 seconds to evaluate whether or not the remnants are oily. None of these instructions allowed participants to consume the candy.

Next, some participants were informed they had completed the task. Other participants were not informed they had completed the task. Regardless, participants then answered various items on a questionnaire, while the candy lay nearby. The amount of candy they spontaneously consumed was measured subtly. Finally, participants completed a measure that assesses their prevailing level of self control, with items like "I am good at resisting temptation".

According to the researchers, people who report an elevated level of self control are more likely to perceive the task as fun or intrinsically rewarding: That is, these participants tend to enjoy opportunities to achieve. Completion of these tasks should vitalize these individuals, increasing their capacity to resist the candy. In contrast, people who report limited self control are more likely to perceive the task as an obligation or burden: These participants do not enjoy difficult opportunities to achieve. Completion of these tasks will deplete the mental energy of people, compromising their capacity to resist the candy later.

The results supported these hypotheses. When people with elevated levels of self control believed they had completed the evaluation task, they felt a sense of vitality, manifested as an inclination to resist temptations to consume candy. Conversely, when people with low levels of self control believed they had completed the evaluation task, they felt depleted, unable to resist this temptation.

The other studies extended these findings. One study showed that high self control, coupled with completion of a task, subsequently enhanced the capacity of individuals to persevere on a tedious task rather than merely resist temptations. Conversely, low self control, coupled with completion of a task, subsequently impaired the persistence of individuals.

As another study demonstrated, when participants with high self control also construe a task as an obligation to work, completion of these activities subsequently impaired resistance to temptation and persistence. That is, in one condition, participants were asked to specify the minimum number of Skittles or M&Ms they will need to evaluate these products. This minimum number is, obviously, less than is the number they might want to consume. Therefore, this instruction imposes a standard or constraint, perhaps invoking a sense of obligation. When this sense of obligation was imposed, even participants with high self control demonstrated less resistance to temptation or persistence after completing the evaluation task. A similar pattern of results was observed when tangible rewards were offered; that is, rewards increased the likelihood that a task will be perceived as an obligation.

Conversely, when participants were informed the task will be fun, even participants with low self control felt a sense of vitality after completing the evaluation task. A cursory allusion to the enjoyment of this task was sufficient to enthuse participants, subsequently enhancing resistance to temptation.

Overall, if tasks were perceived as incomplete, depletion was negligible. That is, incomplete tasks did not seem to undermine subsequent self control. Presumably, while individuals undertake an activity, mechanisms that mobilize the requisite effort are more likely to be operating. One practical implication is that tasks that demand self control, such as weight loss, should never be conceptualized as a circumscribed activity but should be perceived as an ongoing endeavor. Conversely, if a task is fun, construing this activity as complete will enhance motivation.

These findings also reconcile two distinct perspectives: the assumption that motivation depends on availability of a scarce resources and the assumption that motivation is fostered by the fulfillment of fundamental needs. The first assumption is consistent with ego depletion. The second assumption is consistent with self determination theory. Specifically, extrinsic motivation tends to deplete resources, whereas intrinsic motivation tends to elicit vitality, fostering exploration and growth (Ryan & Deci, 2008).

Strength of temptation and the critical level model

According to the critical level model, people may overestimate the impact of intense stressful events and underestimate the impact of modest stressful events (Gilbert, Lieberman, Morewedge, & Wilson, 2004). Consequently, in response to intense stressful events, people mobilize considerable effort to resolve negative emotions. In response to modest stressful events, people do not dedicate the same level of effort to alleviate these unpleasant feelings. The upshot of this possibility is that intense stressful events may be accommodated more effectively than modest stressful events, reducing the likelihood of persistent or strong negative emotions.

Kroese, Evers, and De Ridder (2011) extended this critical level model to the domain of self control. Specifically, individuals are likely to assume that a very attractive temptation, like an exquisite cake, will demand significant discipline and self control to resist. They will, therefore, mobilize the effort that may be needed to resist this temptation. Over time, individuals learn to associate these strong temptations with attempts to regulate behavior and demonstrate discipline.

In contrast, individuals may assume that a modest temptation, such as an ordinary cake, will not demand appreciable self control to resist. They might, as a consequence, not mobilize enough effort to resist this temptation. Therefore, modest temptations might be less likely to be successfully shunned.

Kroese, Evers, and De Ridder (2011) conducted a series of studies to apply the critical level model to the resistance of temptations. In the first study, participants were female students who wanted to lose or maintain their weight. They were all instructed to read excerpts of text and identify spelling errors. Some participants read excerpts that referred to rich, intense descriptions of delicious chocolate, representing a strong temptation. Other participants read excerpts that alluded to factual information about chocolate, representing a weak temptation.

Next, participants completed a lexical decision task, in which strings of letters were presented in sequence. They were told to press one button if the string was a legitimate word in English and another button if the string was not a legitimate word. Three of the words related to dieting: slim, dieting, and diet. If participants had been exposed to a weak rather than strong temptation, they were more likely to recognize words that relate to dieting rapidly. Presumably, the goal to diet was especially salient in these individuals (Kroese, Evers, & De Ridder, 2011).

Study 2 was similar, except participants were exposed to photographs of very attractive or modestly attractive chocolate cakes?-to represent a strong and weak temptation respectively. Again, when the cake was modestly attractive, participants recognized words that relate to dieting more rapidly: That is, the goal to diet was more salient and accessible.

In Study 3, participants were instructed to evaluate the taste of a cake. Some participants were asked to taste a cake that seemed especially appealing, representing a strong temptation. Other participants were asked to taste a cake that seemed modestly appealing, representing a weak temptation. Participants were asked to cut a piece of this cake and then consume this piece, supposedly to evaluate the cake. If the cake seemed modestly appealing, participants tended to cut a larger piece, representing impaired resistance to temptations.

Neurophysiological underpinnings

Some research indicates that dopamine and noradrenaline may restore the resources that underpin self-control. In particular, according to Sripada, Kessler, and Jonides (2014), to maintain self-control, individuals need to suppress or inhibit the default network--a network of brain regions that is active when people are not engaged in a specific task. This default network tends to activate thoughts that are extraneous to the tasks or goals of individuals. The suppression of this network, therefore, contains these distractions and improves self-control.

According to Sripada, Kessler, and Jonides (2014), the dorsolateral prefrontal cortex and the anterior cingulate are vital to the regulation of this default network. In essence, these regions underpin self-control. After individuals complete a demanding task, and hence deplete the resources that underpin self-control, activation of these regions dissipates and hence the default network evokes irrelevant thoughts and other distractions. In contrast, increases in the release of dopamine and adrenaline facilitate the activation of these regions and, therefore, essentially restore self-control.

Sripada, Kessler, and Jonides (2014) conducted a study that validates these arguments. Participants completed two tasks. During the first task, a series of words was presented. To deplete resources that underpin self-control, some participants were instructed to press a button whenever the word comprised an e unless this e was alongside or two locations away from a vowel--a challenging task. In the control condition, to maintain these resources, participants merely pressed the button whenever the word comprised an e. Next, participants completed another task that assessed self-control. On each trial, three numbers appeared, such as 2 1 2. Participants needed to press one of three buttons. In particular, they pressed the button that corresponded to the identity, but not the position, of the unique number. In this instance, they would press button 1 and not button 2.

In addition, before completing these tasks, half the participants received methylphenidate, or Ritalin, to increase the release of dopamine and noradrenaline. The other participants received a placebo.

Some key results emerged. First, as hypothesized, when the first task was challenging, participants did not perform as well on the subsequent activity. Yet, this effect was not observed if methylphenidate had been administered: dopamine and noradrenaline thus seemed to restore the resources that underpin self-regulation.

Second, variability of reaction times was subjected to spectral analysis. After completing the challenging task, frequencies between 13 and 37 a second, called the slow 4 band, was pronounced. This range tends to coincide with the default network. Methylphenidate, however, curbed this range. These results indicate that dopamine and noradrenaline seem to suppress the default network after resources had been depleted.

In many instances, managers need to ensure that employees can regulate their inclinations--and engage in activities or demonstrate tendencies that diverge from their inherent inclinations. To improve this capacity, managers first need to ensure that temptations to engage in unsanctioned behaviors are removed. For example, suppose employees are not permitted to use the internet during a specific period of the day. They should, therefore, not be granted access to computers that are connected to the internet; otherwise, they will need to suppress their temptation to access the internet

Second, employees should not be told to display specific emotions when they interact with customers. That is, in many organizations, employees are instructed, for example, to exhibit happiness and composure, while suppressing frustration or agitation, during these interactions. To fulfill this demand, they need to mobilize their self control. Instead, participants should merely be informed of some practices that temper any negative emotions. They could, for example, be told that frustration and agitation might dissipate if they observe themselves in this setting, from the perspective of a senior manager.

Third, at regular intervals, employees should be granted the opportunity to engage in a task that is challenging but exciting--difficult but feasible. These challenging, exciting, and fun activities tend to restore the resources that can be applied to inhibit natural impulses. Perhaps, twice a day, individuals could attempt puzzles or watch videos--puzzles and videos that are enjoyable and fun, but nevertheless facilitate their acquisition of skills.

Controversies

Learned industriousness: The effect of more than one demanding task

According to Converse and DeShon (2009), most research into the notion of ego depletion applies the same procedure. First, half the participants complete one task that demands self control, depleting a limited supply of resources. The other participants complete a task that depletes fewer, if any, of these resources. Next, participants complete a second task that also demands these resources. If they complete the task that demands considerable self control, their performance on the second activity deteriorates. This cardinal finding implies that individuals cannot devote appreciable effort into some activity if these resources had been consumed by a previous task.

Nevertheless, as Converse and DeShon (2009) maintain, if individuals complete two distinct activities that demand considerable self control, their capacity to devote effort to a subsequent task actually improves rather than deteriorates. Specifically, after individuals complete two or more demanding activities, they develop the expectation that subsequent tasks will also tax such effort, a theory called learned industriousness (see Eisenberger, 1992; Eisenberger & Masterson, 1983; Eisenberger & Shank, 1985). As a consequence, they mobilize more effort to subsequent tasks.

To illustrate, in one study, participants completed a series of three tasks. First, individuals were instructed to uncover subtle differences between pairs of pictures. Second, they completed a series of mathematics questions. Finally, they were asked to unravel a set of anagrams. These anagrams, unbeknownst to participants, were actually unsolvable.

Participants were more likely to persist on the anagrams, demonstrating considerable effort and dedication, when the previous two tasks were difficult rather than simple (Converse & DeShon, 2009). Presumably, because the first two tasks were especially demanding, participants elevated the level of effort they assumed they need to apply subsequently. Hence, they devoted more effort to the anagrams.

In another study undertaken by Converse and DeShon (2009), some participants completed a taxing clerical task--crossing out every e in a document, unless a vowel appears one or two letters ago--before undertaking a test of their comprehension. Other participants completed the same two tasks. However, interspersed between these two tasks, they also completed a difficult Stroop task. That is, participants had to specify the color of words that represented incongruous hues, such as the word red written in blue ink.

Consistent with ego depletion theories, the demanding clerical task compromised subsequent performance on the comprehension test. Nevertheless, as predicted by the theory of learned industriousness, this problem did not arise when a difficult Stroop task was interspersed between these activities (Converse & DeShon, 2009).

These findings imply the level of effort or discipline that individuals can devote to a task depends on two factors. First, if one previous activity depleted the resources that are needed to maintain self control, less effort can be dedicated to subsequent tasks. Second, and in contrast, if several previous activities demanded considerable effort, individuals bolster the energy and exertion they expect to direct to subsequent tasks. This expectation can even override the deleterious effects of ego depletion. Nevertheless, to form this expectation, at least two demanding, but distinct, tasks need to be undertaken in sequence to establish a pattern (see Eisenberger, Masterson, & McDermitt, 1982).

The strength model of self-control versus the conflict monitoring theory

Most scholars agree that completing one task that demands self-control or effort tends to compromise the performance of a subsequent task that demands self-control or effort. Yet, two main theories have been posited to explain this finding.

The first, and perhaps the most prominent, theory--the strength model of self-control (Baumeister et al., 2007)--assumes that one task depletes mental energy from a single resource. Inadequate energy is thus available to facilitate the second task.

The second theory, called the conflict monitoring theory (Dewitte, Bruyneel, & Geyskens, 2009; Robinson, Schmeichel, & Inzlicht, 2010), assumes the first task instills tendencies that undermine performance on the second task. For example, in the first task, participants might learn they should refrain from a response when a green word appears. In the second task, they might learn to press a bar when a noun appears in any color. If, during the second task, a noun appears in green, they experience the conflicting tendency to refrain from a response, learnt during the previous task, or press the bar. To resolve this conflict, they need to register the conflict, underpinned by the anterior cingulate cortex, and then inhibit the incorrect response, underpinned by the prefrontal cortex. This process demands time and can, therefore, impair performance.

As Wenzel, Conner, and Kubiak (2013) highlighted, both theories can explain the finding that positive emotions diminish the detrimental effect of one demanding task on the performance of a subsequent demanding task. According to the strength model of self-control, positive emotions may replenish mental energy, facilitating performance on the second task. According to the conflict monitoring theory, positive emotions may enhance flexibility, increasing the capacity of individuals to override the inclinations they developed during the first task as they complete the second task, curbing the conflict between two subsequent activities.

Wenzel, Conner, and Kubiak (2013) showed the benefits of positive emotions can be ascribed to the conflict monitoring theory instead of the strength model of self-control. Specifically, in a pair of studies, participants completed two tasks in sequence, both of which demand self-control. In one condition, both of the tasks were the same, such as two Stroop tasks, in which individuals need to name the font color of words that represent other colors, such as the word red written in green font. In the other condition, the tasks were different, such as a thought suppression task followed by a Stroop task.

Positive emotions improved performance on the second task, but only if this activity differed from the first task. That is, positive emotions seemed to enhance the capacity of individuals to override the inclination they developed during the first task as they complete the second task. Positive emotions did not seem to replenish mental energy; otherwise these emotions should have enhanced performance on the second task even if this activity was the same as the first task.

Alternative strategies

Direct forgetting

To override habits, people could attempt to invoke self-control. This self-control or effort, however, may deplete resources from a limited supply. Another approach that may be effective is called direct forgetting, as recommended by Dreisbach and Bauml (2014).

Direct forgetting was first uncovered in the context of episodic memory. In this paradigm, participants learn a list of items, such as common nouns. Next, participants receive a cue or instruction either to retain the list or forget the items. Then, participants learn a second list before attempting to recall the first list. If participants had been told to forget the first list, they are not as able to recall these items later. Somehow, the attempt to forget the items diminished the extent to which the words were associated with the context or setting in memory.

According to Dreisbach and Bauml (2014), a similar paradigm could be used override habits as well. In their study, German participants completed three blocks of trials. In each trial of the first block, one of four German words was presented, such as cloud, finger, bell, and chair. Two of the words were grammatically masculine, and two of the words were grammatically feminine. In response to the masculine words, participants pressed the Y key with their left finger. In response to the feminine words, participants pressed the M key with their right finger. In the second block, participants repeated this procedure, but with four different words. Furthermore, on this occasion, the masculine words were associated with the right finger, and the feminine words were associated with the left finger. In the final block, all eight words were included; on this occasion, half the words corresponded to the same finger as the previous blocks; half the words corresponded to a different finger.

In one condition, however, after the first block, the computer supposedly crashed. Participants received an apology and were told to forget what they had learned. This instruction was effective: These participants could readily adjust during the third block. For example, if they used the left finger to respond to the word cloud in the first block, they could readily use the right finger to respond to the word cloud in the third block.

These findings do not imply that implicit memory can be abandoned readily. In contrast to the decline in habits, implicit memory is not specific to particular contexts. Perhaps direct forgetting merely diminishes the extent to which people associate a response to a specific context.

Cialdini, R. B., & Kenrick, D. T. (1976). Altruism as hedonism: A social development perspective on the relationship of negative mood state and helping. Journal of Personality and Social Psychology, 34, 907-914.